CareerCup

Just store these numbers in an array and add two numbers by performing addition on cells....like -

int[] add(int[] A, int[] B){
       int m = 0;
       if(A.size >=B.size){
           m = A.size;
       }else{
          m= B.size';
       }
       int[] result = new int[m+1];
       int index = m;
       int carry =0;
       (iterate both arrays from last to first element, till both array reach at first element){ 
           int x = A[i] +B[j] + carry;
           carry = x/10;
           int number = (x % 10);
           result[index] = number ;
       }
       return result;
}

Take the inputs as string and store them into integer arrays and perform addition something like below:
public class SumOfLargeNumber {
public static void main(String[] args) {
String a = "111111111111";
String b = "22222222222222";
int i = 0;
int firstInputLength = a.length();
int secondInputLength = b.length();
int sizeOfResult = firstInputLength > secondInputLength ? firstInputLength: secondInputLength;
int result[] = new int[sizeOfResult + 1];
int input1[] = new int[sizeOfResult];
int input2[] = new int[sizeOfResult];
while (i < firstInputLength) {
input1[sizeOfResult - i - 1] = Character.getNumericValue((a.charAt(firstInputLength - i - 1)));
i++;
}
i = 0;
while (i < secondInputLength) {
input2[sizeOfResult - i - 1] = Character.getNumericValue(b.charAt(secondInputLength - i - 1));
i++;
}
sumOfInputs(input1,input2,result);
}
private static void sumOfInputs(int[] input1, int[] input2, int[] result) {
int carry=0;
int sizeOfInputs=input1.length;
for(int i=sizeOfInputs;i>0;i--){
int sum = input1[i-1]+input2[i-1]+carry;
result[i]=sum%10;
if(sum/10>10)
carry=1;
else
carry=0;
}
result[0]=carry;
for(int i=0;i<=sizeOfInputs;i++)
System.out.print(result[i]);
}
}

public class CalculateLongIntegers {
	public static void main(String[] args){
		String s1 =  "123456278798238093532765432662476427646456353425635454854";
		String s2 = "1234562787982380935327654326624764276464563534248758758756";
		char[] c1 = s1.toCharArray();
		char[] c2 = s2.toCharArray();
		int[] c3;
		c3 = add(c1, c2);
		if(c3[0] != 0){
			System.out.print(c3[0]);
		}
		for(int i =1; i< c3.length; i++){
			System.out.print(c3[i]);
		}
	}

	private static int[] add(char[] c1, char[] c2) {
		int l1 = c1.length;
		int l2 = c2.length;
		int len = l1 > l2 ? l1: l2;
		int[] result = new int[len+1];
		int i = c1.length-1;
		int j = c2.length-1;
		int carry = 0;
		while(i >= 0 &&j >=0){
			result[len] = (c1[i] - '0' + c2[j] - '0' +carry) % 10;
			carry = (c1[i]-'0' + c2[j]-'0' + carry)/10;
			i--;
			j--;
			len--;
		}
		while(i>=0){
			result[len] = (c1[i] -'0' + carry) %10;
			carry = (c1[i] -'0'+ carry) /10;
			i--;
			len--;
		}
		while(j>=0){
			result[len] = (c1[j]-'0' + carry) %10;
			carry = (c1[j]-'0' + carry) /10;
			j--;
			len--;
		}
		return result;
	}
}

public static int [] add(String a, String b){
		char [] chs_a = a.toCharArray();
		char [] chs_b = b.toCharArray();
		int m = chs_a.length>=chs_b.length? chs_a.length:chs_b.length;
		int [] result = new int [m+1];
		int carry = 0;
		int i = chs_a.length-1, j = chs_b.length-1;
		while (i>=0&&j>=0){
			result [m--] = ((chs_a[i]-'0') + (chs_b[j]-'0') + carry) %10;			
			carry = ((chs_a[i]-'0') + (chs_b[j]-'0') + carry)/10;			
			i--;
			j--;
		}
		
        while (i>=0){
        	result [m--] = (chs_a[i] -'0' + carry)%10;
        	carry = (chs_a[i] -'0'+ carry)/10;
        	i--;
        }
        
        
        while (j>=0){
        	result [m--] = (chs_b[j] - '0'+ carry)%10;
        	carry = (chs_b[j] -'0'+ carry)/10;
        	j--;
        }
		
        if (carry!=0){
        	result [m--] = carry;
        }
				
		return result;

}